C3 Gasification of Biomass

Question 1

difference between combustion and gasification

Answer 1

• combustion has 4 stage (drying, devotilization, combustion of votiles, combustion of char)
  -produce CO2,H2O,NOx,SOx
• gasification has 2 stage (drying , devotilizion)
  -produce CO,H2,N2,H2S

Question 2

process in gasification

Answer 2

1. drying
2. pyrolysis
3. combustion
4. reduction

Question 3

Drying zone

Answer 3

• biomass contain 5-35% moisture
• heated at 100-200 °C to reduce moisture <5%
• ↑ energy efficiency achived when biomass has ↓ intrinsic moisture

Question 4

prolysis zone

Answer 4

• in absence O2
• temp 200-700 °C because large structure
• large molecule (bioplymer) break down into votile medium & solid char
• medium molecule decompose to smaller molecules

Question 5

partial combustion zone

Answer 5

• heterogenous & highlky exothermic reaction
• use gasifying agent (O2,H2O)
• temp 1200-1800 °C
• product CO2,CO,H2O

Question 6

reduction zone

Answer 6

• CO2 + H2O(vapor) reduced by char to produce H2 and CO
• main chemical reaction occur
• remaining solid residue(unwanted char&ash) removed

Question 7

evaluation criterias for gasification performance

4 criterias

Answer 7

1. producer gas (CO&H2) properties
2. gas product yeild
3. carbon conversion
4. efficiencies

Question 8

cold gas efficiency

Answer 8

measure how much of the energy potential in biomass feedstock convert into usable form(syngas)

Question 9

thermal efficency

Answer 9

measure how effectively heat source convert fuel into usable energy
-defined as ratio of amount useful energy producedby system

Question 10

energy efficiency

Answer 10

useful energy output from gasifier

Question 11

cabon conversion

Answer 11

%= [1- (mash × %Cash /100) /
(mbiomass × %C biomass /100) ]×100

Question 12

effect of operating condition on gasification performance

6 effects

Answer 12

1. type,properties&feeding rate of biomass
2. type & flowrate of gasifying agent
3. steam to biomass ratio
4. superficial velocity/recidece time
5. temperature
6. pressure

Question 13

why cellulose produce much lesser H2 than lignin

Answer 13

• cellulose difficult to break bond in cellulose because its more complex(rigid) structure with high degree of polymerization
• thus it require ↑ temp, ↑ residence time to fully gasified
• cellulose tend to form tar & char more than lignin during gasification- ↓gas yeild&efficiency

Question 14

producer gas cleaning impurites

4 types

Answer 14

1. particulates
2. tar
3. N,S &Cl
4. alkali compound